(- Optional step, but the result is the same if this step is omitted: Now I select "Remove disk from virtual drive" -> the "OK" hook disappears and the virtual disc is ejected.)

Now I select a different "Host Drive" (e.g. 'F:' or 'G:'), but there is no "OK" hook visible next to the selected drive and the new Host Drive is not active in the VM.

If I select the original first Host Drive ('E:') the "OK" hook appears again and the drive is active again in the guest VM.

It is however possible to switch from a real physical Host Drive to an ISO by selecting "Choose disk image...".

If I wish to switch to a different real physical Host Drive, I need to shut down the VM guest, select the VM within the "Oracle VM VirtualBox Manager", open "Settings" of the VM, switch to the other physical Host Drive within the "Storage" options and then restart the VM guest.

Change History

It's usually better and faster, if issues get first addressed in the VirtualBox forums, a lot more eyes there. More than 95% of the issues are resolved over there, which keeps the developers focusing on the bug fixes and enhancements, and there is no need for another ticket to keep track of.

Plus a discussion and analysis on the bug tracker is going to help you, me, and potentially a future drive-by user or two. Not so in the forums, many more tend to benefit...